1. Field of the Invention
This invention relates to a hinge device, more particularly to a hinge device with a returning member for automatically closing an open door.
2. Description of the Related Art
A conventional hinge device generally includes a stationary hinge member that is adapted to be mounted on a door frame, and a rotatable hinge member that is adapted to be mounted on a door and that is pivoted to the stationary hinge member so as to permit rotation of the door relative to the door frame between open and closed positions.
One drawback of the aforesaid conventional hinge device resides in that the door needs to be moved manually from the open position to the closed position.
An improved hinge device has been proposed in order to overcome the aforesaid drawback, and includes a biasing member or a hydraulic device interposed between the stationary and rotatable hinge members for automatically closing an open door. However, the biasing member generally closes the door so swiftly such that banging of the door relative to the door frame may result. The hydraulic device employed in the improved hinge device may reduce the effect of banging, but includes too many components that complicate assembly and mass production of the same.
The object of this invention is to provide a hinge device with a returning member for automatically closing an open door and that is capable of overcoming the aforesaid drawbacks of the conventional hinge devices.
Accordingly, a hinge device of the present invention includes a stationary hinge member, a rotatable hinge member, a cam mechanism, and a biasing member. The rotatable hinge member is pivoted to the stationary hinge member so as to rotate about a vertical axis between open and closed positions. The cam mechanism includes a rotatable cam element that is coupled to the rotatable hinge member so as to rotate about the vertical axis together with the rotatable hinge member and that is formed with a first cam face, and a slidable cam element that is formed with a second cam face associated with the first cam face and that is movable in an axial direction along the vertical axis. The second cam face moves away from the first cam face when the slidable cam element is cammed by the rotatable cam element upon rotation of the rotatable hinge member from the closed position to the open position by an external force applied on the rotatable hinge member. The biasing member is connected to the slidable cam element so as to accumulate a returning force when the second cam face moves away from the first cam face and so as to urge the second cam face to move toward the first cam face when the external force ceases to be applied on the rotatable hinge member, thereby returning the rotatable hinge member from the open position to the closed position.